Up to now, the suspension of endless track vehicles, such as snowmobiles, consists solely of springs mounted at the front and at the back of the endless track. In a snowmobile, the ratio of the weight of the passengers to the weight of the vehicle is very high, for instance a ratio of 1/1 as compared to a ratio of 3/20 for a passenger vehicle. In a snowmobile, the spring suspension must be strong enough to support the maximum load intended to be carried by the vehicle. Such spring suspension is normally very stiff and is the cause of frequent back aches suffered by passengers of snowmobiles, especially so since such vehicles negotiate rough terrains. Conventional snowmobile suspensions also cause poor traction on slippery ground, since the endless track often fails to closely follow the ground contour.